.. _`Partition List Predicate`:

.. _`org.sysess.sympathy.list.partitionlistpredicate`:

Partition List Predicate
````````````````````````

.. image:: partition_list.svg
   :width: 48


Partition a list using a configured item-based predicate.




Documentation
:::::::::::::

This node takes a predicate function (a function that returns True or
False) from the configuration and uses it to decide how to partition the
output.

The function is applied once for each input element in the list. If it
returns True, then the element is written to the first output, otherwise it
is written to the second output.

Examples with port type == [table] and item type == table:

    Put tables with more than 10 rows in the first output port::

        lambda item: item.number_of_rows() > 10

    Put nonempty tables in the first output port::

        lambda item: not item.is_empty()

The name of the argument is not important.

See https://docs.python.org/3/tutorial/controlflow.html#lambda-expressions
for a description of lambda functions. Have a look at the :ref:`Data type
APIs<datatypeapis>` to see what methods and attributes are available on the
data type that you are working with.


Definition
::::::::::


Input ports
...........

    **list**  [<a>]
        List


Output ports
............

    **list_true**  [<a>]
        List of items where predicate returned true

    **list_false**  [<a>]
        List of items where predicate returned false




Configuration
.............

    **Partition function** (predicate)
        Function, called for each item in `list` to determine its output partition. Should return a boolean





Related nodes
.............

* :ref:`org.sysess.sympathy.list.grouplist`




Examples
........

* :download:`Predicates.syx </Examples/Sympathy/Generic/List/Predicates.syx>`




Implementation
..............

.. automodule:: node_filter_list
    :noindex:

.. class:: PartitionListPredicate
    :noindex: